[sledge] Substitute out alias of option when including Monad_syntax

Summary:
Otherwise there is an alias `'a t` for `'a option` polluting the
global namespace, which causes e.g. merlin to produce confusing types.

Reviewed By: jvillard

Differential Revision: D20831349

fbshipit-source-id: dff7b4f15

sledge/lib/import/option.ml

@@ -15,8 +15,6 @@ let pp fmt pp_elt fs = function
 let cons xo xs = match xo with Some x -> x :: xs | None -> xs
 
 module Monad_syntax = struct
-  type nonrec 'a t = 'a t
-
   let ( let+ ) x f = map ~f x
   let ( and+ ) x y = both x y
   let ( let* ) x f = bind ~f x

sledge/lib/import/option.mli

@@ -13,4 +13,4 @@ val pp : ('a_pp -> 'a -> unit, unit) fmt -> 'a_pp -> 'a option pp
 
 val cons : 'a t -> 'a list -> 'a list
 
-module Monad_syntax : Monad_syntax with type 'a t = 'a option
+module Monad_syntax : Monad_syntax with type 'a t := 'a option